The invention relates to a facility for the gasification of carbon-containing feed materials, e.g. tar, tar sand, plastics waste, residues from paper and pulp production, residues from the petrochemical industry, electronics scrap and light shredded fractions, and in particular of biogenic feed materials, e.g. harvest waste, energy plants (Mishanthus) or wood chips. The facility serves, in particular, for producing combustible gases with a calorific value of at least 8 000 to 10 000 kJ/m3.
The energy-related utilization of the abovementioned feed materials, at present, is largely limited to combustion. The gasification technologies are set up predominantly for producing weak gases with a calorific value of below 6 000 kJ/kg. These gases, however, are not suitable for utilization, for example, in gas turbines or fuel cells.
In order to produce gases with a calorific value of 8 000 to 10 000 kJ/m3, so-called allothermic gasification has to be carried out. For this purpose, it is necessary for the fuel which is to be gasified to be fed sufficient external heat at a high temperature level of 500 to 900 degrees Celsius, which up until now has involved high technical outlay.
A significant widely used gasification process is the fluidized-bed process. This process may also be used to operate relatively small installations cost-effectively, but does not produce any high-calorie gases. For allothermic gasification in fluidized beds, essentially the following processes and facilities are currently undergoing testing.
Batelle Gasifier
In the case of the Batelle gasifier (two-stage fluidized-bed gasification), the reaction heat for the fluidized bed is produced in an external fluidized-bed combustion operation. The heat is transmitted by exchange of the hot sand bed and thus involves high technical outlay, see Peter Jansen, Thermische Vergasung von nachwachsenden Roh-und organischen Reststoffen [Thermal gasification of renewable raw materials and organic residues]; Institutsberichte der Bundesanstalt fur Landwirtschaft. [Reports of the federal institute for agriculture], Brunswick, 1997.
DMT Gasifier
In the DMT gasifier, a considerable amount of the heat which is necessary for the gasification is to be introduced in that use is made of steam, at a temperature of 750° C., which is superheated for the fluidizing operation. In addition, for the gasification of biomass, the intention is for heat-exchanger pipes to be directed through the fluidized bed, the flue gas with a temperature of 1 150° C. flowing through said pipes. It is barely possible, with the current state of knowledge, to verify that this facility can achieve calorific values of approximately 10 000 kJ/kg. Facilities which operate by this principle are disclosed in U.S. Pat. No. 5,064,444 and U.S. Pat. No. 5,439,491.
In order to increase the chemical conversion, attempts have thus been made to increase the introduction of heat into the fluidized bed by the use of pulse combustors, as is disclosed in U.S. Pat. No. 5,306,481. This method basically allows a relatively high level of heat introduction and thus a chemical conversion which is necessary for allothermic gasification. The use of pulse combustors, however, involves relatively high outlay.
Furthermore, U.S. Pat. No. 4,160,720 discloses a facility which is intended for the gasification of tar sand and in the case of which heat is transmitted into the reaction chamber by means of heat pipes. In the case of this facility, the tar sand runs through the reaction bed and the combustion zone. Since the pyrolysis gas mixes with the flue gas, there is a reduction in the calorific value of this gas, which is not suitable for direct use for gas turbines or for fuel cells.